DESCRIPTION: After falling to a low of 1.74 in 1976, the total fertility rate (TFR) in the United States has since moved upward, reaching 2.08 in 1990, the highest figure recorded since the end of the baby boom. In 1998, the most recent year for which data are available, the TFR was 2.06. Over the same time span, the volume of immigration (both legal and unauthorized) to the United States has steadily increased, with the result that by the end of the 1990s immigration was adding about 900,000 net new residents to the population annually. Moreover, new immigrants have increasingly come from countries with higher levels of childbearing than the United States. As a consequence of these changes, nearly 1 in 5 U.S. births in 1998 (19.5 percent) occurred to a foreign-born mother. When these children of immigrants are considered together with immigrant children (foreign-born children of immigrant parents), nearly one-fourth of young children in the United States now have foreign-born parents. These trends raise significant scientific and policy-related questions about the relative contributions of immigration and immigrant fertility to overall U.S. fertility. Our proposed research has three broad objectives. First, we will use multiple data sources and estimation methods to measure period fertility (the total fertility rate) by nativity, national origin, generational status, and race/ethnicity. Many of these measures are unavailable from standard sources, and they are critical to an adequate assessment of levels and changes in immigrant fertility over the past thirty years and their contributions to other fertility changes. We will assess the consistency of our new fertility measures for immigrant subpopulations by comparing the results of several alternative estimation approaches, and we will gauge the adequacy of the approaches and (in those cases where vital statistics allow it) by comparing more aggregated measures to those based on vital statistics data. Second, we will carry out demographic decompositional analyses in order to assess the extent to which changes in nativity and immigrant national origin composition over the past thirty years have contributed both to changes in differential fertility by nativity, racial/ethnic status, and generational status and, through such shifts, to changes in overall U.S. period fertility. Our analysis of period fertility will also include investigation of the tempo and quantum components of TFR changes. Third, based on the fact that measures of cumulative fertility include both children of immigrants and immigrant children, we will carry out demographic decompositional analyses in order to assess the extent to which changes in nativity and national origin composition have contributed to changes in both of these components of differential and overall cumulative fertility. The results of these analyses, by shedding light on the relative contributions of compositional and rate changes to changes in the numbers of children of immigrants and of immigrant children, will help to clarify the direct and indirect implications of immigration for U.S. fertility rates and for trends in the numbers and composition of children.